More and more layers of fat are forming on your baby's body (not even all those gymnastic routines are enough to compete with the nutrition gained from the placenta) which helps build strength and also helps to keep Baby warm. Babies are unable to regulate their body temperature properly until about 9 months of age, so you'll need to keep this in mind once your little one has arrived. Once your unborn baby has enough fat, the lanugo hair (and some vernix caseosa) will start to deteriorate, as it's no longer necessary.
Your baby's senses are going through some fine tuning, and the hearing and eyesight becomes much better, although they're still not a patch on what they'll be at a few months old (you'll be surprised at how quickly your baby can notice things you'd rather they didn't, such as the TV controller or your bowl of cereal!). Once your baby's born, their hearing might actually be a little worse than it is in utero, as orifices can become a bit clogged with amniotic fluid. This will clear out within a few days.
As your baby's lungs are developing, you'll probably be noticing more and more hiccups. You can usually tell the difference between movements and hiccups as movements are more severe and random, whereas hiccups are gentle and rhythmic. Have the video camera at the ready, it's amazing watching your stomach jump up and down!